Supercapacitor engine starting system with charge hysteresis

ABSTRACT

An internal combustion motor assembly, including an internal combustion motor, a starter and a battery. In addition, the motor assembly includes a capacitor assembly, a capacitor charging assembly and a conductive network, logic and controlled switching assembly adapted to place the internal combustion motor into one of a set of states. This set includes a first state in which the capacitor assembly is receiving charge from the capacitor charging assembly but is not electrically connected to the starter; a second state in which the capacitor assembly is electrically connected to and powers the starter; and a third state in which both the battery and the capacitor assembly are electrically connected to and power the starter. The logic and controlled switching assembly places the internal combustion motor assembly into the third state after it has been in the second state and a set of criteria is met.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of application Ser. No. 10/876,389,filed Jun. 25, 2004, now U.S. Pat. No. 7,319,306, issued Jan. 15, 2008.

BACKGROUND OF THE INVENTION

The development of the supercapacitor (ie., a capacitor of greater than200 Farads) has resulted in the use of capacitors as stores of electricenergy for starting automotive engines. A fairly early example is U.S.Pat. No. 5,146,095, issued to Tsuchiya et al. Here a supercapacitor ischarged up as the automobile driver turns his key to start his vehicle.Then the charge on the supercapacitor is used to start the automobileengine. This procedure avoids the strong current draw from the batterythat is otherwise necessary every time an automobile is started.

One disadvantage of this mechanism, however, is that the vehicle usermust wait for the supercapacitor to be charged up every time he startshis automobile. Also, there is a possibility that the engine will notstart, given the amount of energy stored in the capacitor. Furthermore,it appears that if the capacitor were broken and unable to accept a fullcharge, that the vehicle operator would be left with a nonfunctionalvehicle.

Although a number of other references exist detailing the use of asupercapacitor in starting an internal combustion engine, none of thesereferences detail a system that both avoids an intense current draw fromthe battery at first starting up an engine and that almost neverrequires the automobile user to wait when first starting his automobile.

SUMMARY OF THE INVENTION

In a first separate aspect the present invention is an internalcombustion motor assembly, including an internal combustion motor, astarter and a battery. In addition, the motor assembly includes acapacitor assembly, a capacitor charging assembly and a conductivenetwork, logic and controlled switching assembly, adapted to place themotor assembly into one of a set of states. This set includes a firststate in which the capacitor assembly is electrically connected to andreceiving charge from the capacitor charging assembly, but is notelectrically connected to the starter; a second state in which thecapacitor assembly is electrically connected to and powers the starter;and a third state in which both the battery and the capacitor assemblyare electrically connected to and power the starter. The conductivenetwork, logic and controlled switching assembly places the internalcombustion motor assembly into the third state after it has been in thesecond state and any one of a predetermined set of criteria sets is met.

In a second separate aspect, the present invention is an internalcombustion motor assembly including an internal combustion motor, astarter, a capacitor adapted to, at least in part, power the starter,and a capacitor charging assembly adapted to charge the capacitor. Inaddition, a capacitor charging control element is adapted to control thecapacitor charging assembly so that the capacitor is charged to a firstvoltage and is later recharged to the first voltage whenever its voltagedrops below a second voltage that is at least 0.5 volts lower than thefirst voltage.

In a third separate aspect, the present invention is an internalcombustion motor assembly including an internal combustion motor, abattery, a starter, a capacitor adapted to, at least in part, power thestarter, and a capacitor charging assembly adapted to charge thecapacitor. In addition, a capacitor charging sensing and control circuitis adapted to detect a condition in which the capacitor has at leastsome impairment in its ability to accept charge and is adapted torespond to this condition by switching the motor assembly to a state inwhich the capacitor is not used to power the starter.

In a fourth separate aspect, the present invention is an internalcombustion motor assembly including an internal combustion motor, astarter, and a capacitor charging assembly adapted to charge thecapacitor to a first voltage level. In addition, a manual engine startactuator is adapted to permit an operator to activate the starter and acapacitor low voltage starter lockout system disables the actuator whenthe capacitor is not charged to a predetermined voltage.

The foregoing and other objectives, features and advantages of theinvention will be more readily understood upon consideration of thefollowing detailed description of the preferred embodiment(s), taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an internal combustion motor assemblyaccording to the present invention.

FIG. 2 is a flow chart of a scheme of operation of the motor assembly ofFIG. 1, according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Referring to FIG. 1, a preferred embodiment of the present inventionincludes an internal combustion motor assembly 10. Conventional itemsincluded in assembly 10 include a motor 12, a starter 14, an alternator20 and a motor start actuator 22 for permitting a vehicle operator tostart the motor 12. In addition, a battery assembly 16 and a capacitorassembly 18 include one or more batteries and capacitors, respectively.In addition, a DC-to-DC converter/controller 26 is controlled by aninternal logic unit 40, which is also a part of a conductive network,logic and controlled switching assembly 28. The starter 14 is providedwith electrical power in accordance with a predetermined scheme,discussed below, implemented by assembly 28.

Also included in assembly 28 and controlled by unit 40 are abattery-to-starter relay 42 and a capacitor-to-starter relay 44. Anelectrical system actuator 46 is used by a vehicle operator to activatethe vehicle electrical system, prior to starting the motor. A“wait-to-start” light 50 advises a vehicle operator to not press thestart actuator 22, in accordance with criteria described below.

FIG. 2 illustrates the operation 100 of assembly 10 by logic unit 40.When the electric system is first activated (block 102), unit 40 checksto see if the capacitor voltage, V_(c), is above the minimum voltage forstarting the motor, V_(min), required for the present temperature (box103). At below 0° c., V_(min) is equal to 29 Volts and at greater than0° c., V_(min) is equal to 24 Volts. The temperature may be measuredeither at the logic unit 40, at capacitor assembly 18 or at motor 12. Inone preferred embodiment logic unit 40 receives temperature measurementsboth from motor 12 and from capacitor assembly 18 and sets V_(min) onthe basis of the temperature reading from motor 12, as this is the bestindication of how much energy will be required to start motor 12.

If V_(c) is below V_(min), the start actuator 22 is disabled and the“wait to start” light 50 is activated (block 104); then theconverter/controller 26 charges the capacitor assembly 18 (block 106)until a voltage, V_(max), is reached (box 108). V_(max), similar toV_(min), is a function of the temperature measured at that time. In onepreferred embodiment V_(max) is 28 Volts at greater than 0° C., and 30Volts at below 0° C. In one preferred embodiment all logic measurementsare taken at logic unit 40. In another preferred embodiment atemperature measurement taken at the capacitor assembly 18 determinesV_(max) because the maximum voltage to which a capacitor can be chargedis inversely related to temperature. After V_(max) is reached, theconverter/controller 26 stops delivering current to capacitor assembly18, the engine start actuator 22 is enabled and the “wait to start”light 50 is deactivated (box 110). At this point, motor 12 is ready tobe started and the assembly 10 waits for a start engine signal fromactuator 22.

When a “start engine” signal is received (box 116), logic unit 40 closesthe capacitor relay 44 (along with the starter solenoid), causing thecapacitor assembly 18 to power the starter 14 (block 118). After thestarter 14 has been driven by the capacitor assembly for a time period,T_(BT), (box 120) of typically less than a second, the logic unit 40commands the battery relay 42 to close, causing the battery assembly 16to assist the capacitor in the further process of engine starting (block122). For below freezing temperatures T_(BT) equals 0.35 seconds, whileat above freezing temperatures T_(BT) is effectively set to infinity,with the battery not being utilized to help start the engine.

In this manner, at below freezing temperatures the battery assembly 16assists the motor 12 starting process but is not subjected to thedestructive large current draw that is necessary in the first few tenthsof a second of the starting process. Logic unit 40 then waits for themotor to start (box 124) before opening relays 42 (at below freezingtemperatures) and 44 (block 126).

At this point V_(c) is again compared with V_(min) and if V_(c) issmaller then is charged again (block 104 through block 110). In thissequence, V_(c) will typically reach V_(max) while the engine is runningand typically will continue above V_(min) until the next engine startcommand is received. When this is the case, the engine may be startedimmediately, without waiting for the capacitor to be charged up. Only ifat the time the electrical system is actuated (block 102) so much chargehas bled from the capacitor assembly 18 that V_(c) is below V_(min),must the vehicle operator wait through a capacitor recharge sequence.

A capacitor recharge at electrical system actuation is more likely atbelow freezing temperatures, as the hysteresis is only 1 Volt in thistemperature range. This is acceptable, however, because an electricheating element engine warm up sequence, typically taking far longer toaccomplish than the capacitor charge sequence, must typically occur atthese temperatures. Consequently, the capacitor charge operation doesnot cause an actual delay to the vehicle operator. The fact that in mostinstances the motor 12 can be started without a delay, when desired, isa major advantage of this preferred embodiment.

The converter/controller 26 is able to detect if electric current isflowing to capacitor assembly 18. If capacitor assembly 18 is notaccepting electric current at voltages below V_(max), then thiscondition is noted (a “fault” is set) by logic unit 40 and capacitorassembly 18 is effectively taken out of the circuit, with no furthercapacitor charging being effected and without the use of the capacitorassembly 18 in engine starting. Subsequently, when the ignition isenabled again, the fault is cleared and a further attempt is made tocharge the capacitor assembly 18. If it again does not accept charge,the fault is reset.

The terms and expressions that have been employed in the foregoingspecification are used as terms of description and not of limitation.There is no intention, in the use of such terms and expressions, ofexcluding equivalents of the features shown and described or portionsthereof, it being recognized that the scope of the invention is definedand limited only by the claims which follow.

1. An internal combustion motor assembly including an internalcombustion motor, a starter, a capacitor adapted to, at least in part,power said starter, a capacitor charging assembly adapted to charge saidcapacitor and a capacitor charging control element adapted to controlsaid capacitor charging assembly so that said capacitor is charged to afirst voltage and is later recharged to said first voltage whenever itsvoltage drops below a second voltage that is at least 0.5 volts lowerthan said first voltage.
 2. The internal combustion motor assembly ofclaim 1 wherein said second voltage is less than or equal to said firstvoltage minus one volt.
 3. The internal combustion motor assembly ofclaim 1 wherein said first voltage is greater if a temperaturemeasurement is below a temperature threshold than if said temperaturemeasurement is above said temperature threshold.
 4. The internalcombustion motor assembly of claim 1 wherein the difference between saidfirst voltage and said second voltage is greater if a temperaturemeasurement is below a temperature threshold than if said temperaturemeasurement is above said temperature threshold.
 5. The internalcombustion motor assembly of claim 1 wherein said second voltage isgreater if a temperature measurement is below a temperature thresholdthan if said temperature measurement is above said temperaturethreshold.
 6. The internal combustion motor assembly of claim 1 whereinthe difference between said first voltage and said second voltage isgreater if a temperature measurement is below a temperature thresholdthan if said temperature measurement is above said temperaturethreshold.
 7. An internal combustion motor assembly including aninternal combustion motor, a battery, a starter, a capacitor adapted to,at least in part, power said starter, a capacitor charging assemblyadapted to charge said capacitor and a capacitor charging sensing andcontrol circuit adapted to detect a condition in which said capacitorhas at least some impairment in its ability to accept charge and adaptedto respond to said condition by switching said motor assembly to a statein which said capacitor is not used to power said starter.
 8. Aninternal combustion motor assembly including an internal combustionmotor, a starter, a capacitor charging assembly adapted to charge saidcapacitor to a first voltage level, a manual engine start actuator,adapted to permit an operator to activate said starter and a capacitorlow voltage starter lockout system that disables said actuator when saidcapacitor is not charged to a predetermined voltage.
 9. The motorassembly of claim 8 wherein said predetermined voltage varies as afunction of a temperature measurement.